1. Field of the Invention
The present invention relates to a drain collecting apparatus for a semiconductor fabrication system, and more particularly to an improved automatic drain collecting and exhausting apparatus for a semiconductor fabrication system which enables discharge of drained chemicals such as organic solvents from the system.
2. Description of the Prior Art
As shown in FIG. 1, a conventional automatic drain collecting and exhausting apparatus for a semiconductor fabrication system includes a drain collector 2 for temporarily storing discharged drainage from a semiconductor fabrication system 1 when a process is completed.
In the conventional apparatus, a low sensor 3 and a full sensor 4 are connected to an outside wall of collector 2, each sensing a level of drainage output from fabrication system 1. Adjacent to drain collector 2, a drain tank 5 is provided for storing the drainage transmitted from drain collector 2. A plurality of tubes connect drain collector 2 and drain tank 5, enabling drainage flow therebetween.
A connection structure for linking drain collector 2 and drain tank 5 includes: a first tube 6 connecting drain collector 2 to a port of an air pump 9 via a first air valve 11, a second tube 7 connecting air pump 9 to drain tank 5, and a third tube 8 connecting drain tank 5 to the exterior via a second air valve 12.
A first sub-tube 6a connects a thinner container 17 to a portion of first tube 6 that is positioned between first air valve 11 and air pump 9. A second sub-tube 7a is connected, via a valve 14, to a portion of second tube 7 that is positioned between air pump 9 and drain tank 5. Reference numeral 15 denotes an alarm sensor, reference numeral 16 denotes a full sensor, and reference numerals 11a, 12a, 13a denote air springs for supporting respective air valves 11, 12, 13.
The operation of the above-described conventional drain collecting and exhausting apparatus for a semiconductor fabrication system will now be described.
The level of drainage discharged from the system 1 and collected in drain collector 2 increases as a semiconductor fabrication process is repeated in the system 1. At some point, full sensor 4 is actuated in response to the increasing level of discharged drainage. When full sensor 4 is actuated, the first air valve 11 is opened. Air pump 9 creates an air pressure difference which causes the drainage stored in drain collector 2 to be transmitted through first and second tubes 6, 7 to drain tank 5.
When a sufficient amount of drainage is transmitted from drainage collector 2 to drain tank 5 and a drain level in drain collector 2 is lowered, the low sensor 3 attached to the outside wall of drain collector 2 becomes actuated to open the third air valve 13. When third air valve 13 is opened, thinner in the thinner container 17 flows into air pump 9 for a predetermined time (about 5 to 10 seconds), diluting any high viscosity drainage in the air pump 9. The second air valve 12 is subsequently employed to exhaust the drainage from drain tank 5 to the exterior.
The above-described drain collecting and exhausting apparatus for the conventional semiconductor fabrication system experiences frequent air pump breakdown. Following each such breakdown, the drainage must be manually collected and exhausted, during which time the fabrication system 1 is rendered inoperable.
Further, due to frequent inactivation of the full sensor and the low sensor, the drainage collector can easily overflow, effectively contaminating the surroundings of the system and increasing the amount of thinner required.
Still further, the conventional system is expensive since the ratio of the system to the drain collecting apparatus is approximately 1:1 or 2:1.